1. Field of the Invention
The present invention relates to an apparatus and method to restore a signal using minimum value sampling, and more particularly, to a signal restoring apparatus and method using minimum value sampling, which are capable of effectively preventing deterioration of a restored signal caused by aliasing occurring when minimum value sampling of an input signal is performed in order to restore a signal.
2. Description of the Related Art
In general, a depth mapping apparatus is an apparatus recording spatial depth and distance information of a subject in units of pixels, unlike a camera. In other words, while an ordinary camera records an image by recording the intensity of a subject with respect to each pixel, the depth mapping apparatus records a distance to the subject with respect to each pixel.
A method that is most widely used in order to record a depth map is radiating light to a subject and measuring a time of flight (TOF) that is taken by the light to return after being reflected by the subject. The depth mapping apparatus measures a time taken by the light reflected by the subject to arrive at a photo detector with respect to each pixel. Here, if a plurality of rays is returning to a pixel of the photo detector after being reflected by the subject, the depth mapping apparatus chooses a ray having a shortest TOF to determine a distance from the pixel to the subject.
More specifically, as illustrated in FIG. 1A, a depth mapping apparatus 11 radiates light 13 to a subject 12, and when the radiated light 13 is reflected by the subject 12 and returns, the depth mapping apparatus 11 selects a ray having a shortest TOF to determine a distance to the subject 12 from the pixel. The selected distance is referred to as a minimum distance sample (MDS) or a minimum value sample (MVS). As illustrated in FIG. 1B, a minimum distance of a hull surrounding the subject 12, which will be abbreviated to an MDH, is obtained from the MDS or MVS of each pixel.
Meanwhile, from sample values sampled through the minimum distance sampling or minimum value sampling, the depth mapping apparatus 11 can generate a spatial model in relation to the subject 12. Here, as illustrated in FIG. 2, in a process of generating a spatial model of the subject 12 using the depth mapping apparatus 11, first, minimum distance sampling or minimum value sampling of a depth map 21 with respect to the actual distance to the subject 12 is performed and thus an MDH 22 is obtained.
Also, when the depth mapping apparatus 11 generates a spatial model of the subject 12, a depth map 23 is restored through the obtained MDH 22. Here, the depth map 23 is restored to have values shorter than actual distance values to the subject 12. This is because aliasing, such as a staircase phenomenon, occurs when the MDH 22 is obtained through minimum distance sampling or minimum value sampling. This aliasing can be a critical defect when a depth map is restored, and in order to compensate for this aliasing, a restored depth map requires further restoration. In order to reduce this aliasing, a method of increasing the resolution of the depth mapping apparatus 11 is used.
If the resolution of the depth mapping apparatus 11 is increased, the aliasing phenomenon decreases but the staircase phenomenon occurs due to the principle of operation. Accordingly, increasing the resolution is not a fundamental solution. Accordingly, a method used by the depth mapping apparatus 11 to restore a depth map using sample values considering the aliasing phenomenon is needed.
Japanese Patent Laid-Open Publication No. 2001-067465 discloses an interpolation method to obtain interpolation data by performing second sampling after obtaining discrete data through first sampling of convex discrete data. Though the method provides a method of obtaining interpolation data by generating integrated values, mean values, and approximate values of convex data in intervals of second sampling, a method of preventing deterioration occurring due to the aliasing phenomenon when a depth map is restored has not been suggested yet.